Laminated glass is being used for both windows and for architectural glass. Recent acts of terrorism in the form of bomb attacks on buildings have led to renewed efforts to design transparent facades that mitigate injuries and structural damages from blast loadings and fires. Transparent facades are desirable in security areas wherein a large vision area is required.
It is further desirable to have walls and doors which are either substantially transparent or partially transparent to be resistant to fire which may occur separately or from an explosion.
Previous efforts to provide security laminates have been either to provide wire glass, i.e. wire embedded in a glass laminate which provides resistance to shock shattering and to hold the glass sheets together longer when exposed to fire and heat. However, it does not hold splinters or slivers of glass brought about by impacting and fracturing wire glass. Moreover, vision is impaired by the use of the wire glass.
An advancement in the wire glass laminates as disclosed in U.S. Pat. Nos. 2,659,686 and 5,219,630 is to provide an interlayer of plastic to hold the glass in place when broken or splintered.
Other methods to mitigate damages from blasts is to form laminates of glass and/or plastic by the use of mass and an interlayer or interlayers by use of a suitable interlayer such as polyvinyl butyral or an ionomer. However, such structures still lack the resistance necessary for incendiary blasts or fires.
U.S. Pat. No. 5,002,820 to Bolton et al, which is herein incorporated by reference discloses laminated safety glass having thick glass and intermediate film layers which prevent spall of larger pieces on impact.
The use of so-called safety glazing or penetration resistant glazing for windows, windshields, and the like using multiple layers of polycarbonate, glass and other resinous materials is well known. For example, glass-polycarbonate resin laminates are described in U.S. Pat. Nos. 4,663,228 and 3,666,614.
In U.S. Pat. No. 3,520,768 there are described laminates of relatively thick glass having a comparatively thin polycarbonate film as the adhesive layer. While generally useful, these laminates suffer from an inability to withstand multiple shots, especially when struck by high velocity bullets such as those fired from rifles.
U.S. Pat. No. 4,125,669 to Triebel et al discloses a laminated safety glass which utilizes a thick outside layer of silicate glass which is bonded to a polycarbonate pane of at least 1.5 mm thick.
U.S. Pat. No. 4,312,903 to Molari discloses impact resistant, double glazed structures comprising a plurality of laminae selected from polycarbonate, glass and solid resinous materials. The glass laminae faces the direction of impact and has a thickness from about 30 to 220 mils. The structure utilizes relatively thick outward layers and relatively thin inward layers.
It is understood that the term “plastic” applies to both “polymeric film” and “polymeric sheet” and the term “layer” applies a single film or sheet or a laminate of two or more films or sheets.
It is desirable to provide doors which are either substantially or partially comprised of transparent laminates with fire resistance.
It is also desirable to provide fire resistance to walls which are entirely comprised of glazing material or partially.